Are we talking about the expanded view? If so, click on Artwork which is near the top left of the main panel. Select Customize (or perhaps customize panel) and then towards the middle on the right click on more settings (or show settings) which is specifically for the expanded view. I'm pretty sure that's where you can add a third (and perhaps fourth) line. Note that my instructions are coming from my memory as I don't have MB in front of me at this point.